WETTING-DRYING EFFECT OF EXPANSIVE SOILS AND ITS INFLUENCE ON SLOPE STABILITY

The wetting-drying effect of expansive soils plays an important role in slope stability analysis. This paper uses the field monitoring data of moisture contents of expansive soil slope and the calculation results of atmospheric influence depth at Nanling region. It then determines the wetting-drying circulate amplitudes of laboratory experiments. Laboratory tests on the soil strength are performed to discuss on the wetting-drying effect of expansive soil. Furthermore, the stability of expansive soil slope is studied taking into account the wetting-drying effect. The results show that the cohesion of expansive soil decreases with increasing number of cycles and its impact is especially obvious during the first and second cycles. After that, it reaches to a constant state. However, the friction angle keeps a stable value with little influence of the wetting-drying effect. It is also found that the value and cyclic number of the constant state reduce with increase of amplitude of variation of water content. As wetting-drying cycles cause irreversible damages to soil intergranular links, the shear strength reduction of expansive soil is the result of micro-structural degradation. Furthermore, the slope stability and safe factor decrease with increasing number of cycles and the stability analysis method with considering the wetting-drying effect is more in line with the practical engineering.